The high voltage, coupled with their high energy density, has made
lithium ion batteries the standard. But lithium is expensive and
can develop breaches in its internal structure, a condition known
as dendrite growths, which can cause the batteries to catch fire.
As an earth-abundant resource, magnesium is cheaper and does not
form dendrites. Until now, however, it has been held back by the
need for a better cathode -- the electrode from which the current
flows -- and more efficient electrolytes, the medium through which
the ionic charge flows between cathode and anode.